1. Field of the Invention
The present invention relates to a device for fastening a shoe on a bicycle pedal.
2. Description of the Prior Art
In particular in patents, there have already been proposed a number of different devices of this type which permit on the one hand easy positioning of a shoe on a bicycle pedal without any manual intervention and on the other hand rapid disengagement of the shoe either at will (when the cyclist desires to place his foot on the ground) or automatically as a result of a fall.
French Pat. No. 2,422,175 relates to a device of this type in which the pedal is equipped with shoe-retaining means adapted to cooperate with a mounting support fixed to the sole of the shoe in order to maintain this latter applied on the pedal. These retaining means comprise fixed front means and movable rear means urged into their shoe-retaining position by a resilient system.
Positioning of the shoe on the pedal takes place in two stages : a forward movement of approach which brings the mounting support to a position in which it is abuttingly applied against the front retaining means and a downward movement of the heel in which the mounting support engages by snap action within the rear retaining means. Intentional disengagement is performed by means of a lateral twisting movement of the foot which initiates opening of the rear retaining means.
This device is very satisfactory from an operational standpoint. Practical tests performed on prototypes have in fact proved that positioning of the shoe on the pedal and disengagement of the shoe are two extremely easy, rapid and natural operations.
In the embodiments of FIGS. 23 to 25 and 26 of the patent cited earlier, the movable rear retaining means are constituted by a single lever pivotally mounted on a transverse horizontal shaft (which is parallel to the axis of rotation of the pedal) and actuated by a spring which is placed in a longitudinal position. The pivoted lever is provided either with a pair of claws or with a single claw adapted to cooperate with the mounting support by means of surfaces which form a V when seen from above. By means of a wedge effect, lateral displacement of the mounting support thus produces a rearward pivotal movement of the retaining lever and consequently releases the shoe.
The construction just mentioned is particularly advantageous by reason of its extreme simplicity and its low cost price which are essential requirements for large-scale manufacture and wide commercial distribution. Furthermore, the transverse arrangement of the pivotal shaft of the lever ensures free and reliable withdrawal of the retaining claw (or claws), thus permitting instantaneous release of the shoe at the time of lateral disengagement. However, this construction is subject to the following major disadvantage : while the bicycle is traveling, the efforts exerted by the mounting support on the pedal during one revolution are successively oriented in the forward, downward, rearward and upward directions. In point of fact, the rearwardly direction efforts which may be relatively violent on certain occasions (starting, climbing hills by standing up on the pedals, for example) produce direct action on the retaining lever in the direction of opening of this latter. In consequence, these efforts are liable to produce untimely disengagement of the shoe with respect to the pedal, which is clearly unacceptable from the point of view of both safety and performance.